| When loosening the coal seam in the Harwusu open-pit coal mine,the size of the coal block formed is too large or too small,which will directly affect the economic benefits of the mine.When the blasting intensity is high,the size of the coal block formed is small,which leads to dust pollution,which seriously threatens the health of the workers and the local ecological environment.When the blasting intensity is low,the size of the coal block formed is large and the second is broken.The cost increases and the difficulty of moving is increased.These two aspects seriously restrict the sustainable development of the Harwusu open-pit mine.In order to respond to the theme of green safe and efficient mining of open pit mines,it is necessary to conduct an accurate evaluation study on the blasting block degree of the Harwusu open-pit mine and optimize the corresponding blasting parameters.Based on fractal theory analysis method,combined with GGS formula,exponential comparison method and partial differential method,the fractal model of explosive ore rock mass distribution is obtained.By means of fractal theory,photogrammetry technology and computer image processing technology,The method for deriving N(x)has developed the "automatic and fractal test system for burst size distribution".According to the stress wave attenuation theory,the fracture zone model of the surrounding coal seam after explosive explosion is established,and the dissipation law of the explosion stress wave in the propagation process is revealed.Using the Separate Hopper Pressure Tester(SHPB)test,the relationship between the blasting load and the applied load of the indoor specimen impact failure test was established,and the impact load of the coal rock sample with the air pressure from 0.13 MPa to 2.0MPa was carried out.The test,based on the high-speed camera system,qualitatively describes the dynamic failure morphology of coal rock samples.At the same time,the direct distribution measurement method is used to obtain the block distribution characteristics after the sample is destroyed.Based on the fractal dimension,the dynamic fracture characteristics of coal and rock samples in SHPB test were quantitatively described,and the fractal dimension characteristics of the specimens after fracture were obtained.According to the particle size range,the broken pieces were divided into three groups: large diameter,medium diameter,and powder.The variation of mass fraction of coal and rock fragments with three pressures was analyzed.The two principles of blasting evaluation are given.The pressure range of the indoor impact load test is deduced to be 0.30 MPa ≤ P < 0.90 MPa.Using the digital calculation method,the coal seam blasting block degree image recognition system was built,and the blasting block degree between the two blasthole areas on the site was firstly identified and identified twice,and the distribution characteristics of the coal seam blasting block were obtained.In addition,according to the fractal dimension calculation method,the fractal dimension of the on-site coal rock blasting block degree is obtained.Based on the comprehensive indoor impact load test and on-site coal seam blasting block analysis,the blasting range of the single-hole blasting zone division was calculated.Based on this range,two optimization methods for increasing the blast hole spacing and row spacing and reducing the explosive amount were proposed and simulated by ANSYS/LS-DYNA software.The results show that the mass percentage of granular coal decreases under the two conditions.8.36% and 5.71%,the lump coal rate increased by 2.04% and 1.39% respectively.The optimization effect brought by the increase of the blast hole spacing and the row spacing is better and better.The paper has 66 pictures,34 tables,and 130 references. |
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